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In June 2007 after the 2005 BP Texas City incident, American Petroleum Institute Recommended Practice (API RP) 753, “Management of Hazards Associated with Location of Process Plant Portable Buildings”, was published. In addition, a 3rd Edition of API 752 was released in 2009 to address the Texas City incident, OSHA comments, and NEP findings.  The revised API RP 752 and new API RP 753 included several changes that would impact industry’s approach to facility siting, one of which was adding language specifying that thermal and toxic risk should be reviewed as part of facility siting.  However, very little guidance was provided on how to do so.

Industrial sites include a wide variety of buildings falling into two main categories: conventional construction (steel-framed, masonry, precast concrete, etc. buildings) and modular construction (trailers, shipping containers, and Blast Resistant Modular (BRM) steel buildings).  Buildings at modern facilities and new buildings for aging facilities should be designed with facility siting and personnel protection in mind.  Buildings using conventional construction are specifically configured for their purpose and can be designed to resist the loads associated with most potential hazards, although not all construction materials are suitable for all hazards.  Reinforced concrete construction certainly provides the greatest inherent capacity against blast, fragment thermal and toxic hazards.  BRMs can also be designed to resist most blast loading conditions, and being of modular construction, can efficiently be installed on-site. While API RP 752 and 753  provide a good starting point for location of personnel on site, there is a heavy bias towards protecting against vapor cloud explosion events.  As a result, the design of buildings at industrial facilities has typically focused on the structural response of building components to blast loads and not on the vulnerability associated with building occupants to a full range of hazards including fragment, thermal, and gas ingress (flammable and toxic) in addition to blast.  Therefore, there is a disconnect between “hazard resistant buildings” and the actual protection afforded to occupants, which can result in unknowingly placing personnel in buildings that afford inadequate protection.

To see a case study on new building selection based on specific hazards, request the BakerRisk paper presented by KarenVilas at the Mary Kay O’Conner Process Safety Center 22nd Annual International Symposium in October 2019: Are biases towards the recent past causing us to unintentionally expose personnel to increased levels of risk?

FORTRESS Design and Performance

The design for blast resistant buildings is usually performed by specifying a design blast load and performing a dynamic analysis to verify that the response of all structural components meets pertinent response limits.  However, this type of structural analysis ignores secondary impacts non-structural components may have on building occupants.  In addition, this design approach does not address other potential hazards that are present in facilities with blast hazards.

FORTRESS has been designed to ensure that occupants of the building are not subjected to life threatening hazards.  These hazards include:

  • Significant structural deflections, approaching incipient failure or structural collapse
  • Generation of internal debris, both from damaged structural components and from non-structural items commonly found in building (items attached to walls or roofs such as light fixtures, cabinets, ducts, or wall finishing)
  • Significant heat rise that would be hazardous to occupants or would heat interior items producing smoke or toxic fumes
  • Leakage of toxic or flammable gases from the building exterior

The capacity of the building is designed and tested for the following performance criteria:

  • Blast: 8psi overpressure at >> 200 ms (long duration)
    • Negligible occupant vulnerability
    • ASCE Low Response
  • Fragmentation: 13 lb projectile at 171 ft/s (116 mph) velocity
    • Local spalling observed
  • Thermal: 1-hour direct impingement for ¼-inch saturated propane jet fire
    • Local spalling observed on building structure, but internal air temperature <110F and negligible smoke/toxic offgas
  • Toxic: <0.1 ACH infiltration for main building and <0.03 ACH infiltration for interior Shelter-In-Place (SIP) room
    • SIP Control Box, designed and engineered to provide system specification
  • Extreme Weather: Resistant to high wind and debris from hurricane and tornado natural hazards

For more information on how FORTRESS is the best market solution for your facility siting needs, contact us today.

FORTRESS Wall Panel Shock Tube Testing of Blast Capacity
FORTRESS Wall Panel and Door Installation Impinged Jet Fire Testing
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